Choline acetyltransferase (ChAc) catalyzes the synthesis of acetylcholine in the cholinergic nervous system. Recently this enzyme was purified for the first time in our laboratory from bovine caudate nuclei. We propose to continue work on this preparation along two different paths: (1) Localization of ChAc: to map the cholinergic neurons and pathways in the brain, brain stem, and spinal cord using frozen sections and antisera to the purified enzyme. (2) Characterization of ChAc: to study the enzyme with the aim of elucidating its physicochemical and kinetic properties.